# 1.1 Skills practice exam 2: chapters 3, 4, 5, & 6

Questions 1 – 2 refer to the following: Below is the probability distribution function for the number of high school years that students at a local high school play on a sports team.

$X$ $P\left(X=x\right)$
0 0.32
1 0.12
2
3 0.18
4 0.14

What is the probability that $X=2$ ?

• 0.24
• 0.76
• 0.32
• Cannot determine

A

Over the long run, the average number of years that we would expect students at this high school to play on a sports team is:

• 0
• 1.7
• 2
• 2.6

B

According to the 2000 United States Census, 12.3% of the population is Black or African American. The probability that a randomly selected U. S. resident is NOT Black or African American is:

• 0.123
• 0.877
• 0.754
• Cannot determine

B

Assume the statistics final is a multiple choice test with 40 questions. Each question has four choices with one correct answer per question. If you were to randomly guess on each of the questions, what is the probability of getting exactly the expected number of correct answers?

• 0.5839
• 0.5605
• 0.25
• 0.1444

D

In an exponential distribution, the mean is larger than the median.

• true
• false

A

In Fall 1999, students in one Math 10 section determined that the length of movies at the cinema was normally distributed with a mean of 148 minutes and a standard deviation of 19 minutes. Find the third quartile and interpret it.

• 75 minutes; Three-fourths of the movie lengths fall below 75 minutes.
• 160.8 minutes; Three-fourths of the movie lengths fall below 160.8 minutes.
• 160.8; Three-fourths of the movies last 160.8 minutes.
• 75 minutes; Three-fourths of the movies last 75 minutes.

B

Which of the following is FALSE about data that follows the normal distribution?

• The mean is the same as the mode.
• The standard deviation is the same as the mean.
• The median is the same as the mode.
• Most data is within 3 standard deviations of the median.

B

The graph showing the age of getting a driver’s license in California starts and peaks at age 16, and decreases from there. This shape most closely resembles what type of distribution?

• Normal
• Binomial
• Uniform
• Exponential

D

Use the following information for questions 9 and 10. The amount of time that a randomly chosen 6th grade student spends on homework per week is uniformly distributed from 30 to 120 minutes.

What is the probability that a randomly chosen 6th grade student spends at least 60 minutes per week on homework knowing that he/she will spend at most 80 minutes per week on homework?

• 1.20
• 0.6667
• 0.2222
• 0.4

D

What is the expected amount of time that a randomly chosen 6th grade student spends on homework per week?

• 45 minutes
• 60 minutes
• 30 minutes
• 75 minutes

D

Use the following information for questions 11 and 12. The length of time a randomly chosen 9-year old child spends playing video games per day is approximately exponentially distributed with a mean equal to 2 hours.

Find the probability that a randomly chosen 9-year old will play video games at most 3 hours.

• 0.7769
• 0.9975
• 0.0025
• 0.2231

A

70% of 9-year old children will play video games per day for at most how long?

• 0.60 hours
• 2.41 hours
• 0.71 hours
• Cannot determine

B

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At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
how did you get the value of 2000N.What calculations are needed to arrive at it
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